Bosses are being warned about breaking the law by using hidden miniature cameras to spy on staff.

For the use of "pinhole" cameras is in sharp focus after Privacy Commissioner Allan Chiang Yam-wang took a subsidiary of Sun Hung Kai Properties to task for snooping.

Chiang found after an investigation that management subsidiary Hong Yip Service Co breached the privacy ordinance by its "unlawful and unfair collection of personal information."

But Chiang said he will not be penalizing the company as it has dismantled the eye-spy gear.

And Hong Yip bosses continue to claim they were not spying on employees by mounting a camera outside a changing room at a housing estate, and that it was to pick up trespassers in the car park. Still, two security guards had been fired as a result of their snooping.

"Covert monitoring is generally regarded as highly privacy-intrusive," Chiang said. "Employers should not adopt covert monitoring unless it is justified by special circumstances." Reasons can include matters like the theft of confidential data - but only as a last resort.

Warning against secret monitoring of employees, Chiang said overt devices such as CCTV cameras offer a legal alternative that in most cases is just as effective as secret cameras.

According to the investigation, a pinhole camera was installed in a private housing estate - which one remains a secret - in May 2009. In September, Hong Yip managers reviewed pictures and fired two staffers for "lingering

" in the changing room while on duty.

The pair filed a complaint with the privacy commissioner after finding the camera concealed in a metal box on a staircase leading to the changing room.

The director of Hong Kong Human Rights Monitor, Law Yuk-kai, said: "Spying is criminal because when people suspect they are being monitored there can be feelings of insecurity when they're alone. They are unable to enjoy a private life."

Legislator Ip Wai-ming, of the Hong Kong Federation of Trade Unions, said: "Employees aren't working in jail. Hong Yip crossed the line for spying on staff by setting up pinhole cameras at a workplace."

Ng Wai-yee, vice chairwoman of the Federation of Hong Kong and Kowloon Labour Unions, said there have to be efforts to make people aware of workplace rights. "Everyone should be treated fairly and with respect."

Eddy Li Sau-hung, president of the Hong Kong Economic and Trade Association, said employers generally should avoid installing pinhole cameras unless there are security worries - and they should never put cameras around toilets or changing rooms.

And if employers do think it vital to have cameras in offices, he said, "they should inform all employees and obtain consents. It is absolutely immoral for employers to install cameras without informing staff."

The Hong Yip case is not the first controversy about pinhole cameras.

In 2005, Hongkong Post was caught in a row involving six pinhole cameras at one of its branches. Interestingly, Chiang was the head of Hongkong Post then.